Method of producing sodium aluminum sulphate



l sept'. 22,',193a 'A H; FISKE n AL METHOD 0F PRDUCING SDIUM ALUMINUMSULPHATE Filed March 20, 1935' sTATE .steps in the process.

Patented Sept. 22, 1936 UMINUM sULPml'rEA Augustus H.' Fiske, Warren,and Gharles S. Bryan, v Providence, It. I., assignors to RumfordChemical Works, Rumford, B.. I.,

' Rhoseisiana;

acorporationo! V: ,v

j Application March 20, 1935. serial No. 11;97,9

somims. (o1. zs;11s)

In the manufacture of Vsodium aluminumV sulphate to which" ,thissulphates have been generally'heretofore produced as by reacting ahydrated oxide ofv aluminum source in sulphurie acid V(usuallywithjother steps or treatments) and the'c'ombination in said form withsodium sulphate. The excess acid factor of t'hereaction`and otherimpurities, if

any, were then removed by heating and/or by .crystallizing Such methodswere usually'slow. and costly andthe :product obtainable commercially,al-

though Satisfactcry"n in quality,` required large capital to purchaseequipment for the various Such -methods also' required highlytrainedtechnical staffs and gen- ,erally yinvolve the employment of morechemical V. knowledge thanis necessary with ourpresent in vention. l .Y

4The product which we prepare. by our process is known as sodiumaluminum sulphate and is prepared onfa large scale as one of the majorchemical industries by large chemical manufacturers.

Its use is confined almost entirely to the food industry and moreparticularly to its use as an ingredient in baking powder.

Since a food manufacturer or a baking powder manufacturer may notnecessarily have available any considerable technical resources orextensive chemical knowledge, nor be equipped to manufacture sodiumaluminum sulphate by the usual process, our invention enables him toprepare sodium aluminum sulphate of proper quality for food purposes bypurchasing, as raw materials as sources of his sodium aluminum sulphate,substances which can be converted directly into sodium aluminum sulphatewithout having any great chemical knowledge or expensive apparatus.

Instead of starting with the crude ore from which the aluminum oxide isextracted by means of sulphuric acid, as is done on a large scale bymany chemical manufacturers, we can according to our concept start inour process with aluminum sulphate which is manufactured for variouspurposes and available in the Vopen mar- 'invention pertains.' Vsuch numsulphate .inthe equivalent amountspresent in thenished product.

According to our invention `a sodium aluminum sulphate of usual reactivejstr'engthand of great purity and whiteness may be produced by a methodcharacterized by simplicity. Our product andthe methods of producing itare indicatedl generally in the proposition that there is a potentialchemical'reaction `between acid sodium sulphate NaHSOi, and `aluminum l0sulphate A12(SO4)3, under heat.' As villustrative of our inventionV wesubmit the following disclosure and` discussion which we have attemptedto illustrate as to method by"a schematic indication of apparatusandstepsin l the accompanying drawing. A

Our concept was that of a new and simple process for .producing sodiumaluminum suljphate. We were immediately `c'oncerned'with its relationto' baking powder so that without intentv tc limit our rightswe discussour invention :as applied in that field. It is, of course, applicabletootherelds.,V j f a According to our inventions we may take'as oursources, commercial acid sodium sulphate (NaHSO4) and aluminum sulphate(A126003) preferably of a high grade and purity. These we provideusually in a dry state and preferably comminuted so as to be intimatelymixed. This pre-mixture, preferably in finely powdered form we then heatto just below a red heat, which for such material is about 968 F. Inthis heating of the mixture the following reaction presumably takesplace:

During this heating the sulphuric acid is driven off as a vapor andrecovered by condensation as indicated at I-I and I in the diagram. Inthis diagram the hopper A may be provided for the aluminum sulphate andthe hopper B for the acid sodium sulphate. These being preferably in thenely powdered form as above indicated, may be intimately mixed as in ascrew or like 4- mixer C. If not previously pulverulent they may beground together at this point (not indicated). Thus processed they aredischarged conveniently as into a bin D from which they can beccnveniently trucked as by a floor car E to the furnace 50 or mufe Fheated as by a re box G. After firing for a relatively short time oruntil the mix is brought to just below dull red and held only longenough to complete the reaction, the product is discharged from themufile and is ready for grind- 55 ing and other steps usual in thepreparation of such materials as for use in a baking powder.

For example, we may take 33.5 parts by weight Y of aluminum sulphateA12(SO4)3 and dry mix in as about 1400 F. at which point aluminumsul-YCharg'es as of500 lbs. can be phate decomposes. readily controlled as tointernal developments of temperature.

After a reasonable heatreactionthefmaterial is drawn from the retort andallowed to" cool. It

can then be ground and sifted to suitable' neness as foruseiiraJ bakingpowder. A Y .Y n It'is to bented vthat the normal acidic strength of thereaction Vof these ingredientsafter'they have been reacted would be inanyordinary process.calculated,v for example, .in units of equivalentsof'bicarhonat of soda reactiveneutralization. 92r.22'%. In contrast ourmethod' produces aproduct having an actual acidic bicarbonate ofsoda-equivalent neutralizing strength of Y103.32%

after reaction.

This indicates a new and unexpectedv increase in the development oftheacidic value by our process. This is obviously an importantdiscovery'l Y :The resultant sodium aluminum sulphate so produced'isactually available for combination in baking powder at an acidic orAneutralizing value approximately 100% to..110% of its own .weight inbicarbonate of Vsoda units@Y f TheV methodmay be Variedand the Yproductcorrespondinglyvaried as to acidity or reactivity .andlas to itsgranularror' crystalline form which differs from` the two componentsbefore heating. Ally such materialsY and methods are therefore toVbeAconsidered,as comprehended in thefollowing claims.'

sultant product.

What we therefore claim and desire to secure by Letters Patent is:-

1. In a method of manufacturing sodium aluminum sulphate, those stepsconsisting in premixing acid sodium sulphate in finely divided form witha finely divided aluminum sulphate in chemically equivalentproportionsto form sodium aluminum sulphate and in heating the mixtureto @just below a red heat whereby to produce a sulphate of high acidicvalue in the resultant sulphate- 2."*In a method of manufacturing sodiumaluminumsulphate, those steps consisting in premixing dry acid sodiumsulphate in chemically equivalentV proportions to form sodium aluminumsulphate with adr'y aluminum sulphate and in :heatingthemixture to justbelow a red heat to produce 'a high acidic value in the resultantsulphat'e;'.

3. In` a method of manufacturing sodium aluminum sulphate, 'those stepsconsisting in reactingrdry premixed acld'sodium'sulphate and dryaluminum sulphate in chemically equivalent proportions to form sodiumaluminum sulphate by heating to just below al red heat.

`4. In a method of manufacturing sodium aluminumj'su1phate, those stepsvconsisting in reactingdry premixed acid sodium sulphate and dryaluminum sulphate in chemically equivalent proportions to form sodiumaluminumvsulphate by heating to just below a. red heat,V and inconducting away `the sulphuric acid formed by the reaction V5.V In amethod of manufacturing sodium alu- `minumsulphate that step consistingin reactively sintering a premix of dry acid sodium sulphate andaluminum sulphate in chemically equivalent proportions to form sodiumaluminum sulphate toyproduce an intensified acidic value in-the re-AUGUSTUS H. FISKE. CHARLES BRYAN.

